The LRAD corporation says that anyone within a 100 meters of the device’s sound path will experience extreme pain. The version generally utilized by police department (the LRAD 500X) is designed to communicate at up to 2000 meters during ideal conditions. In a typical outdoor environment, the device can be heard for 650 meters. The 500x is also capable of short bursts of directed sound that cause severe headaches in anyone within a 300-meter range. Anyone within 15 meters of the device’s audio path can experience permanent hearing loss.
[…] Use of the device has come under fire because of the potential for permanent hearing loss. Human discomfort starts when a sound hits 120dB, well below the LRAD’s threshold. Permanent hearing loss begins at 130dB, and if the device is turned up to 140dB, anyone within its path would not only suffer hearing loss, they could potentially lose their balance and be unable to move out of the path of the audio. The device is also entirely operator dependent, which could lead to serious ramifications if the officer in charge doesn’t have sufficient training.
Emphasis mine. For people not on the metric system, 15 meters is a little under 50 feet. We don’t know how far they have it turned up, but from here we know that it is obviously enough to be very painful. Most of the time these are deployed, police aren’t afraid of going up close and personal within that range, hurting protesters— which, by the way, include children.